The adjusting force comparison values thereby serve in particular for the identification of failures, such as for example blocking by an external influence, during operation. For this, the current actuating force is detected as a function of the adjusting path of the actuating element during the respective adjusting operation and compared with the associated adjusting force comparison value. If the currently measured value of the actuating force deviates from the adjusting force comparison value at the current actuating element position beyond and in some cases predefined tolerance limit, this is identified as a failure by the control unit. Once a failure has been identified, predefined failure routines can be started.
Adjusting devices thus known are preferably deployed in the field of vehicle engineering, where power-activated adjusting devices are increasingly deployed for example to enhance user-friendliness. Interactions or at least possible points of contact frequently exist here between the adjusting device and people. Particular examples of these are adjustable vehicle windows that can be controlled electromotively, pneumatically or hydraulically, roofs with a slide/lift mechanism, convertible roofs, vehicle doors, cover systems, vehicle seats, personal restraint systems, running gear components or similar moving vehicle components, in land, air and water vehicles.
But the inventive method can also be deployed in other areas of mechanical engineering. Examples of this are operator protection devices on production machines and electrically, hydraulically or pneumatically operated gates, doors, windows of hangars, houses, rooms, enclosures or elevators.
Here it is principally the failures of relevance to personal safety that are protected against with the adjusting operation. Such a failure occurs for example when body parts are trapped between the pane and frame during the automatic closing operation of an electromotively operated window closing system in a vehicle. Personal safety has to be ensured here by limiting the trapping forces during closing operations to a value which cannot result in personal injury.
A window closing system with an anti-trapping safety circuit for automobiles or similar vehicles is for example known from automotive engineering (DE 33 03 590 C2). This window closing system comprises an electronic power meter for continuous measurement of the power input of the drive motor and a storage medium, in which a power-travel diagram is stored. A power tolerance limit is assigned to the power-travel diagram so that if the power exceeds the predefined tolerance limit, the power flow direction at the driving electric motor is interrupted or reversed.
A window closing unit is also known from patent document DE 196 33 941 C2, with which the motor power is used to calculate the drive force, which is recorded in a diagram as a function of the respective travel position and stored in a storage unit, when the closing part, in particular the window or sliding roof, is closed for the first time after manufacture of the vehicle. This means that, during subsequent movement operations of the closing part during standard operation, such a motor power can be set that the motor force corresponds exactly to the friction force required in each instance. The friction force is then increased by the permissible trapping force for final activation of the electric motor of the positioning drive.
Ever more stringent requirements are increasingly being specified for effective anti-trapping protection between a vehicle part closing by means of a motor-driven power activation and a countering barrier. According to said requirements the closing operation must be terminated for example or the window, partition wall or roof component system must be driven in the reverse direction before it applies a force of 100 Newton or more.
The trapping force is thereby defined as the excess drive force, which exceeds the actuating force required to overcome the static and/or dynamic counterforces (e.g. friction force) inherent in the system to adjust the actuating element. Non-linearities in the transmission of force between the drive and the actuating element and fluctuations in the counterforces along the adjusting path mean that a non-constant actuating force is required along the adjusting path, which is designated here as an actuating force graph.
In the case of the device known from DE 196 33 941 C2, an actuating force graph is recorded during the first closing operation and then stored as a friction force/travel diagram in the storage device of the controller and used to regulate the drive. The drive is now controlled so that the overall drive force at each point of the adjusting path corresponds to the actuating force predefined by the friction force/travel diagram plus the predefined value for the maximum permissible trapping force. If the minimum adjusting force required is then reduced after the friction force/travel diagram has been defined, for example due to the run-in response of the transmission mechanism, the trapping force increases by the corresponding value and in some cases exceeds the limit value.
In order therefore to be able to guarantee the required trapping force limit values, it is essential to predefine or determine adjusting force comparison values along the adjusting path as precisely as possible. This is however complicated by the non-linearities in the transmission of power, e.g. of a transmission mechanism, between the drive, e.g. an electric motor, and the actuating element, e.g. a vehicle window. These non-linearities are caused by kinematic factors of the power transmission mechanism as a function of the adjusting path and by friction forces inherent in the system that fluctuate over the adjusting path and counteract the actuating force. A further problem with the precise predefinition or determination of the adjusting force comparison values results from the fluctuations due to the tolerances required by production technology in the friction forces inherent in the system within a production run and the run-in response of the entire kinematic arrangement from the drive unit to the actuating element.